Character mistake: Phoebe gets hit in the head with a tree branch but she puts her hand on the opposite side she was hit on.
Factual error: This is a summer time movie but you can see brown leaves everywhere in the film like its the beginning of fall.
Continuity mistake: When Ally is thrown in the pool she climbs out and sits behind Sean and Molly with soaking wet hair however a couple of shots later her hair has partially dried itself. (00:15:57)
Revealing mistake: After Sean is murdered by decapitation in the shack there are a number of close-up shots of Angela's deceased victims, and if you look closely you can see some of them are moving slightly. (01:04:26)
Deliberate mistake: The photographs that Angela takes off the boys that show the girls naked obviously were not taken outside the cabin, they are far too clear. The fly netting and window would have obscured them. Also, judging by the position of the beds in the photographs it seems like they were taken inside the cabin. (00:32:02)
Continuity mistake: At the pool when Sean and Molly are lying on towels discussing their families there is a shot focused on Molly's face, and she says she has a big family and people refer to them as "The Brady Bunch." In this shot you can see a very distinct blond haired man in the pool behind her. The shot then changes to a wide shot showing both Sean and Molly again and the same distinct blond haired man is now behind them on the other side of the pool. (00:14:54)
Audio problem: In the scenes inside to cabin where Angela keeps her victims you can hear flies, but there are no visible flies anywhere.
Revealing mistake: After Phoebe is hit in the head with the tree log, she falls to the ground, and Angela cuts out her tongue, but no blood drips from Phoebe's mouth.
Other mistake: When Angela starts up the chainsaw (to kill Judd with) we hear the sound of it starting but you can see it is not on. (00:35:54)
Revealing mistake: Toward the end film when the female counselor finds Uncle John dead and a camper hanging, the hanging camper's eyes are shaking as he's trying to keep them open in a certain way.
Answer: It's hard to say why she wants them to eat peas. But she does say that there could be anything in there even poison. My guess is that she might have poisoned the food.